1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method for processing a substrate, and a nozzle that makes droplets collide with a substrate covered by a liquid film. Examples of substrates to be processed include semiconductor wafers, substrates for liquid crystal displays, substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photomasks, ceramic substrates, and substrates for solar cells.
2. Description of Related Art
In a manufacturing process for a semiconductor device or a liquid crystal display, etc., a substrate processing apparatus is used to process substrates, such as semiconductor wafers, glass substrates for liquid crystal displays. A substrate processing apparatus described in Japanese Unexamined Patent Application Publication No. 2011-29315 includes a spin chuck holding a substrate horizontally, a head injecting droplets of a processing liquid toward an upper surface of the substrate from a plurality of discharge holes, and a cover rinse nozzle supplying a cover rinse liquid to the upper surface of the substrate.
The head injects droplets of the processing liquid toward a plurality of collision positions within the upper surface of the substrate. Likewise, the cover rinse liquid nozzle discharges the cover rinse liquid toward a liquid contact position within the upper surface of the substrate. The cover rinse liquid discharged from the cover rinse liquid nozzle spreads along the substrate from the liquid contact position toward the plurality of collision positions. A liquid film of the cover rinse liquid is thereby formed on the substrate and the plurality of collision positions are covered by the liquid film of the cover rinse liquid. The droplets of the processing liquid are injected toward the upper surface of the substrate that is covered by the liquid film of the cover rinse liquid.
A thickness of the liquid film of the cover rinse liquid formed on the substrate decreases with increasing distance from the liquid contact position. With the substrate processing apparatus described in Japanese Unexamined Patent Application Publication No. 2011-29315, distances between the respective collision positions and the liquid contact position are not fixed and variation of liquid film thickness occurs among the respective collision positions. Further, the cover rinse liquid flowing to a collision position at a downstream side with respect to a direction of flow of the cover rinse liquid along the substrate is impeded in its progress by droplets injected onto a collision position at an upstream side, and thus a supply flow rate of the cover rinse liquid differs between the upstream side collision position and the downstream side collision position, thereby further increasing the variation of liquid film thickness. Thus, with the substrate processing apparatus described in Japanese Unexamined Patent Application Publication No. 2011-29315, it is difficult to control the liquid film thicknesses at the respective collision positions to be of a fixed magnitude.
When the liquid film covering the collision positions is thin, a large impact is applied to the substrate by collisions of the droplets and a pattern formed on the substrate may become damaged. To prevent damage, increase of discharge flow rate of the cover rinse liquid from the cover rinse nozzle to increase the liquid film thickness at the respective collision positions may be considered. However, if the liquid film covering the collision positions is thick, impacts applied to particles attached to the substrate decrease and a decrease of particle removal rate may thus occur. There is thus an optimal value of the thickness of the liquid film that covers the collision positions.
As mentioned above, it is difficult to control the liquid film thicknesses at the respective collision positions to be of a fixed magnitude with the substrate processing apparatus described in Japanese Unexamined Patent Application Publication No. 2011-29315, and it is thus difficult to form a liquid film of the optimal thickness at all collision positions. It is thus difficult to perform optimal processing at the respective collision positions.
Also, with the substrate processing apparatus described in Japanese Unexamined Patent Application Publication No. 2011-29315, variation of film thickness (thickness of the liquid film of the cover rinse liquid) occurs among the respective collision positions because the distances between the respective collision positions and the liquid contact position are not fixed. Variation thus occurs in the impact applied to the substrate by the collision of the droplets. Specifically, a large impact may be applied at a certain position within the substrate while a small impact is applied to another position within the substrate. A region in which pattern collapse occurs and a region in which foreign matter is not adequately removed may thus form within the same substrate, and uniformity of processing may thus be lowered.